1. Field of the Invention
The invention relates to an optoelectronic micromodule.
2. Description of the Related Arts
Such an optoelectronic micromodule is known from EP 0 331 331 A1, EP 0 660 467 A1 and DE 43 13 493 A1.
EP 0 331 331 A2 discloses an optoelectronic micromodule having an optical component and a focussing lens. The optical component emits optical radiation in an emission direction perpendicular to a main carrier surface. The focussing lens, which is held by an auxiliary carrier, is arranged above the optical component in the emission direction. In this case, the focussing lens can be displaced by means of the auxiliary carrier in such a way as to enable the beam direction to be adjusted. However, one disadvantage of the arrangement described is that an adjustment of the focussing is not possible by a shift of the focussing lens in or counter to the beam direction.
DE 43 13 493 A1 discloses an optoelectronic micromodule in which an optical waveguide is coupled to a light-emitting element by means of a ball lens. In this case, the ball lens is almost arranged in the emission direction of the light-emitting element. The light-emitting element is fixed on a carrier. The ball lens is positioned in an etched trench formed in the carrier. A shift of the ball lens is not provided, however, in the optoelectronic micromodule described. Consequently, adjusting both the beam direction and the focussing of the ball lens can be carried out only in a complicated manner.
FIG. 1 shows a simplified illustration of the optoelectronic micromodule 101 disclosed in EP 0 660 467 A1.
The optoelectronic micromodule 101 has a substrate 102 having a substrate surface 103, on which a laser diode 104, a monitor diode 105 and a glass prism 106 are fixed. The laser diode 104 emits laser radiation parallel to the substrate surface 103 predominantly in a first beam direction 107 and in a second beam direction 108, the latter being oriented in the opposite direction to the first beam direction 107. The monitor diode 105 is part of a control unit (not shown) for the laser diode 104 and, to that end, is arranged on the substrate surface 103 in such a way that laser radiation emitted by the laser diode 104 in the second beam direction 108 can be incident in the monitor diode 105. The glass prism 106 has a mirror surface 109, which forms an angle of 45xc2x0 with respect to the normal of the substrate surface 103, and is arranged on the substrate surface 103 in such a way that laser radiation emitted by the laser diode 104 in the first beam direction 107 is deflected by the mirror surface 109 from the first beam direction 107 into a third beam direction 110 and, consequently, beam deflection is effected. Said third beam direction 110 is oriented perpendicularly to the substrate surface 103. The glass prism 106 is covered by a lens optical arrangement 111, fabricated in a planar process, with an effective optical region 112 on an area opposite to the substrate surface 103. In this case, the lens optical arrangement 111 is arranged in such a way that laser radiation passes through the effective optical region 112 in the third beam direction 110 and is focussed onto a desired point by said region.
An unsatisfactory optical quality of the focussed laser radiation is achieved by the construction shown in FIG. 1, with the result that typically only a coupling efficiency of approximately 25% is achieved when the laser radiation is coupled into a monomode optical fiber. This is due primarily to the inadequate optical properties of the lens optical arrangement 111 fabricated in a planar process. In the case of the typically high optical aperture of the laser diode 104, the lens optical arrangement 111 exhibits high aberration and, moreover, cannot be fabricated with the required diameter of the effective optical region 112. In addition, the beam deflection is undesirable for many optoelectronic micromodules, for example for optoelectronic micromodules in butterfly housings.
An adjustment of an optoelectronic micromodule which can be effected during operation of the optoelectronic micromodule is referred to as active adjustment.
The invention is based on the problem of providing an optoelectronic micromodule which can be actively adjusted in two dimensions, in which it is possible to dispense with a deflection of the optical beam path and it is also possible to use optical components having high optical quality. In this case, the optical components are provided for influencing light (e.g. focussing, deflection, filtering, modulation, etc.), light being understood to be electromagnetic radiation in the wavelength range from ultraviolet to far infrared.
The problem is solved by means of the optoelectronic micromodule having the features in accordance with the independent patent claim.
An optoelectronic micromodule comprises an optoelectronic component, for example an optoelectronic radiation source, and also a radiation variation unit. The optoelectronic component is fixed on a main carrier and can emit light in an emission direction, the emission direction being directed parallel to a main carrier surface of the main carrier. Furthermore, the radiation variation unit is arranged in the emission direction and fixed to an auxiliary carrier. The auxiliary carrier has an auxiliary carrier surface which is oriented plane-parallel to the main carrier surface and is in touching contact with the latter. Furthermore, the auxiliary carrier is arranged such that it is displaceable plane-parallel to the auxiliary carrier surface relative to the emission direction, thereby enabling two-dimensional adjustment of the radiation variation unit. The radiation variation unit can be adjusted both parallel and perpendicularly to the emission direction.
As an alternative, the optoelectronic component may also emit light in at least two emission directions. It is then advantageous if a radiation variation unit is provided in each emission direction.
Furthermore, a recess may be provided in the main carrier, in which recess the radiation variation unit can be accommodated at least partly such that it is freely moveable during its adjustment without contact with the main carrier.
The recess in the main carrier may also be designed as a through opening.
In a preferred embodiment of the optoelectronic micromodule, a through hole is provided in the auxiliary carrier, in order that the light can leave the optoelectronic micromodule after passing through the radiation variation unit.
Silicon is preferably chosen as fabrication material for both the main carrier and the auxiliary carrier, since the form of the carriers and also of the recesses can be controlled in a specific manner by crystal growth and also preferential etching. Any desired method for crystal growth and also for preferential etching can be used. It is pointed out that silicon carriers can be fabricated with very great precision.
One advantage of the optoelectronic micromodule according to the invention is that the radiation variation unit can be adjusted while the optoelectronic component is emitting, i.e. active adjustment can take place.
In accordance with a first embodiment of the invention, a ball lens may be provided as the radiation variation unit, which ball lens focuses the light emitted by the optoelectronic component through the through hole in the auxiliary carrier for example onto an input end of an optical waveguide.
Instead of a ball lens, however, it is also possible to use other optical components.
In accordance with a second embodiment of the invention, the radiation variation unit is realized by a spherical lens which, just like the ball lens described above, focuses the light emitted by the optoelectronic component through the through hole in the auxiliary carrier for example onto an input end of an optical waveguide.
In a third embodiment of the invention, a planar mirror is provided as the radiation variation unit, which mirror directs the light emitted by the optoelectronic component through the through hole in the auxiliary carrier for example onto an optoelectronic receiver.
A fourth embodiment of the invention envisages that the radiation variation unit can be realized by a focussing mirror. Such a focussing mirror directs the light emitted by the optoelectronic component through the through hole in the auxiliary carrier for example onto an input end of an optical waveguide as well as focuses the light onto said input end.
In accordance with a fifth embodiment of the invention, the radiation variation unit is set up in such a way that a frequency multiplying crystal takes up the light emitted by the optoelectronic component, alters the spectrum of the light and outputs the light altered in this way through the through hole in the auxiliary carrier to a user.
In a sixth embodiment of the invention, a polarizer is provided as the radiation variation unit, which polarizer allows the light emitted by the optoelectronic component to pass through the through hole in the auxiliary carrier only with a specific polarization.
In accordance with a seventh embodiment of the invention, the radiation variation unit is realized by a filter which allows the light emitted by the optoelectronic component to pass through the through hole in the auxiliary carrier after having been filtered in accordance with the filter curve.
Depending on the desired embodiment of the invention with regard to the radiation variation unit, the through hole may be situated at different locations in the auxiliary carrier and also have different cross-sectional forms.
In a further embodiment of the invention, the optoelectronic component is also set up in such a way that it can receive light on at least one side. Instead of at least one emission direction, the optoelectronic micromodule then has at least one receiving direction.
A semiconductor laser diode which emits light of a specific wavelength is preferably chosen as the optoelectronic component. However, it is also possible to use electro-optical filters, optoelectronic semiconductor amplifiers or optoelectronic modulators as the optoelectronic component. Optoelectronic modulators include, for example, electroabsorption modulators, Mach-Zehnder modulators and also laser diodes with monolithically integrated modulators.
Taking account of the optoelectronic component used, the radiation variation unit preferably comprises one or a plurality of optical components.